Semiconductor manufacturing facilities typically utilize a number of buffer storage areas, a number of bays that includes processing tools, an overhead track system, and a number of overhead traveling vehicles or transporters (OHTs). The buffer storage areas store substrate carriers which are also known as front opening unified pods (FOUPs), standard mechanical interface (SMIF) pods, and cassettes.
It is also known to utilize overhead buffer storage systems (aka zero footprint storage) in semiconductor manufacturing facilities. These overhead storage systems are typically suspended from a ceiling in a manner similar to the track system. An OHT can access the overhead buffer storage system via the track and functions to transfer the substrate carriers between, among other locations, the processing tools and the overhead buffer storage system.
However, it sometimes occurs that the control system of the semiconductor manufacturing facility is rendered blind as to the specific location of each substrate carrier. This can occur when the data provided to the control system is lost or corrupted. When this occurs, the OHTs must go out to the areas where the substrate carriers are stored, retrieve each substrate carrier, and deliver it to a data collection area (i.e., one of the floor storage buffer locations or one of the processing tools). These data collection locations have RFID readers which can read the RFID tags of the substrate carriers.
This process is very time consuming and represents time that the facility is not processing wafers, which is, of course, very costly. For example, in a facility having 206 buffer storage locations in three different bays or in a facility having about 300 buffer storage locations in four different bays, one OHT can retrieve and transfer a substrate carrier to a read station in about 2 minutes. This means that the OHT will require 6.8 hours to identify all of the substrate carriers. If two OHTs are used, the OHTs will require 3.4 hours to identify all of the substrate carriers. If an entire fabrication facility with 5000 buffer locations needs to have the substrate carriers read, this can mean that all of the OHTs will be tied up in identifying the substrate carriers instead of delivering product to the processing tools, creating a potential bottleneck for the facility.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described herein.